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Articles 1051 - 1063 of 1063

Full-Text Articles in Physical Sciences and Mathematics

Rotational Excitation Of Polar Molecules By Electrons, Marvin H. Mittleman, Jerry Peacher, Balazs F. Rozsnyai Dec 1968

Rotational Excitation Of Polar Molecules By Electrons, Marvin H. Mittleman, Jerry Peacher, Balazs F. Rozsnyai

Physics Faculty Research & Creative Works

Rotational excitation of polar molecules is calculated in the approximation that the electron transit time is short compared with rotational periods with the result of an E-1 behavior of the cross section. Diffusion cross sections are calculated for Δl=0,1,2. Significant corrections to the Born approximation are obtained for large dipole moments. The range (in energy) of applicability of the result is discussed in terms of the energy dependence of the corrections, and a novel energy dependence of these corrections is encountered and explained.


Modified Phase Representation And Effects Of Inelasticity In N/D Calculation Of P-Wave Pion-Pion Scattering, Barbara N. Hale, Arnold Tubis Oct 1968

Modified Phase Representation And Effects Of Inelasticity In N/D Calculation Of P-Wave Pion-Pion Scattering, Barbara N. Hale, Arnold Tubis

Physics Faculty Research & Creative Works

An N/D formalism based on a modified phase representation is used to study the effects of inelasticity on the ρ-wave pion-pion amplitude. The effects of high-energy inelasticity are introduced in terms of the assumed behavior of the high-energy phase (not phase shift) of the partial-wave amplitude. Using a ρ-exchange input force with the experimental ρ mass and a ρ width of about 100 MeV, and the assumption that the average phase is (1/2)π, for total c.m. energies greater than about 8Mπ, we find that there is no appreciable reduction in the width of the calculated ...


Critical Assessment Of The Polarized-Orbital Method In Atomic Scattering, Marvin H. Mittleman, Jerry Peacher Sep 1968

Critical Assessment Of The Polarized-Orbital Method In Atomic Scattering, Marvin H. Mittleman, Jerry Peacher

Physics Faculty Research & Creative Works

The method of polarized orbitals used in calculating electron-atom scattering amplitudes has two obvious flaws: the wave function is discontinuous, and the method is not variationally based. These are corrected in a somewhat arbitrary manner, and it is found that the results then depend upon a parameter of the theory sufficiently strongly that there are serious doubts about the predictive nature of the theory.


Modified Dispersion Relations And Π Π Scattering, David J. George, Barbara N. Hale, Arnold Tubis Aug 1968

Modified Dispersion Relations And Π Π Scattering, David J. George, Barbara N. Hale, Arnold Tubis

Physics Faculty Research & Creative Works

The ππ S-wave scattering-length predictions of Weinberg have been tested by using dispersion sum rules for the infinite-energy cross section. Reasonable agreement is obtained with the infinite-energy cross section (≈15 mb) estimated from the factorization theorem for the Pomeranchon Regge residues. Experimental phase-shift data of Gutay et al., Walker et al., and Baton et al. are used in estimating the dispersion integrals. The analysis seems to rule out an I = 0 S-wave scattering length ⪞0.4μ-1.


New Superconvergent Dispersion Relations For The Forward Πn Crossing-Even Amplitude, David J. George, Barbara N. Hale, Arnold Tubis Apr 1968

New Superconvergent Dispersion Relations For The Forward Πn Crossing-Even Amplitude, David J. George, Barbara N. Hale, Arnold Tubis

Physics Faculty Research & Creative Works

A Liu-Okubo-type dispersion relation is derived for the crossing-even pion-nucleon forward elastic scattering amplitude T(+). Two subtractions are made, one at the physical scattering threshold and the other at a previously determined zero of T(+) on the imaginary axis of the complex ω (pion lab energy) plane. The dispersion relation is well satisfied over the whole allowed range of the Liu-Okubo parameter. Moreover, it is nearly saturated by low-energy scattering for a considerable range of the parameter. It should thus serve as an extremely sensitive test of the low-energy scattering data when such data become more accurately known.


Associative Detachment: H+Hˉ→₂*+E, Joseph C.Y. Chen, Jerry Peacher Apr 1968

Associative Detachment: H+Hˉ→₂*+E, Joseph C.Y. Chen, Jerry Peacher

Physics Faculty Research & Creative Works

The process of associative detachment in the (H,H-) collision system is investigated at energies below 12 eV. In this energy region, the interaction potential between H and H- has recently been determined. The energy dependence of the cross section is calculated with explicit allowance for the production of "hot" hydrogen molecules. It is observed that associative detachment provides a possible mechanism for generating an inverted population of the residual molecule such as H2.


Interaction Potential Between The Ground States Of H And Hˉ, Joseph C.Y. Chen, Jerry Peacher Mar 1968

Interaction Potential Between The Ground States Of H And Hˉ, Joseph C.Y. Chen, Jerry Peacher

Physics Faculty Research & Creative Works

An investigation of the interaction potential for H and H- in both ungerade and gerade modes is carried out by a semiempirical method in which the recently observed isotope effect in dissociative attachment of electrons to hydrogen molecules is used. The interaction obtained is complex, and the imaginary parts of the interaction account for electron emissions during the course of the interaction. A comparison of the present result with other calculations is presented. The isotope effect in dissociative attachment is also discussed. It is shown that the ratios of the survival probabilities alone do not provide an adequate approximation for ...


Dielectric Properties Of Solid Solutions Of Bifeo₃ With Pb(Ti, Zr)O₃ At High Temperature And High Frequency, Robert Travis Smith, Gary D. Achenbach, Robert Gerson, William Joseph James Jan 1968

Dielectric Properties Of Solid Solutions Of Bifeo₃ With Pb(Ti, Zr)O₃ At High Temperature And High Frequency, Robert Travis Smith, Gary D. Achenbach, Robert Gerson, William Joseph James

Physics Faculty Research & Creative Works

Solid solutions of BiFeO3 with PbTiO3, PbTi0.5Zr0.5O3, and PbZrO3 were prepared. The crystallographic data on these solutions, which are basically perovskitic, are given. The dielectric constants of the materials were determined at a frequency of 0.53 GHz and at temperatures up to 800°C. Dielectric Curie points were found in solutions containing up to 90 mole % BiFeO3. These results leave little doubt that BiFeO3 is ferroelectric or antiferroelectric. The extrapolated Curie point for BiFeO3 is above 850°C. BiFeO3 appears more likely to be ferroelectric ...


Survival Probability In Dissociative Attachment, Joseph C.Y. Chen, Jerry Peacher Nov 1967

Survival Probability In Dissociative Attachment, Joseph C.Y. Chen, Jerry Peacher

Physics Faculty Research & Creative Works

The survival probability in dissociative attachment is investigated with special attention to the (e, H2 ) system. It is shown that the simple expression for the dissociative-attachment cross section, as given by the product of a capture cross section and a survival probability, is equivalent to the s -wave approximation for the g → g dissociative attachment. This expression, however, does not constitute an approximation for the g → u dissociative attachment, since the parity of the initial rotational states of H2 is always opposite to that of the relative angular momentum states of H and H- and the capture cross ...


Rapid Calculation Of Electron Scattering Factors, Jerry Peacher, John G. Wills Jun 1967

Rapid Calculation Of Electron Scattering Factors, Jerry Peacher, John G. Wills

Physics Faculty Research & Creative Works

The phase amplitude method is used to reduce the radial Schrödinger equation to two separate differential equations, one for the phase and one for the amplitude. These functions are both smooth as opposed to the rapidly oscillating solution of the radial Schrödinger equation for electron energies in the kilovolt range. The partial-wave phase shifts were obtained rapidly by integrating the differential equations for the phase and amplitude numerically. Hartree-Fock and Thomas-Fermi-Dirac fields were used in the calculation. Results for argon and uranium are given in order to compare with previous results. It was found that the WKBJ approximation to the ...


Ferroelectric Properties Of Pbzro₃-Bifeo₃ Solid Solutions, Robert Gerson, Pen-Chu Chou, William Joseph James Jan 1967

Ferroelectric Properties Of Pbzro₃-Bifeo₃ Solid Solutions, Robert Gerson, Pen-Chu Chou, William Joseph James

Physics Faculty Research & Creative Works

Solid solutions of BiFeO and PbZrO3 were investigated for crystallographic and dielectric properties. A new pseudocubic perovskite phase was found, which has been tentatively indexed as orthorhombic with the same unit cell as PbZrO3 but with dielectric properties characteristic of a ferroelectric substance. The Curie point in this series of solid solutions has a minimum of about 155°C at a composition of about (PbZrO3)0.80 (BiFeO3)0.20, which at room temperature lies on the boundary between the orthorhombic antiferroelectric and the pseudocubic ferroelectric phases. This composition has a relative dielectric constant of 800 ...


On The Calculation Of Multicenter Two-Electron Repulsion Integrals Involving Slater Functions, Russell A. Bonham, Jerry Peacher, Henry L. Cox May 1964

On The Calculation Of Multicenter Two-Electron Repulsion Integrals Involving Slater Functions, Russell A. Bonham, Jerry Peacher, Henry L. Cox

Physics Faculty Research & Creative Works

Integral transforms are used to evaluate many-center two-electron repulsion integrals involving Slater s-type functions. The reduction of a general four-center integral of this type to a form convenient for computational purposes is presented. The technique described has the important advantage that all lesser many-center and one-center integrals can be obtained from the four-center case by proper choice of constants. The form of the result is such that simple single-precision numerical techniques yield rapid and accurate evaluations of many-center integrals. Several numerical examples are presented.


Theory Of The Effect Of Temperature On The Electron Diffraction Patterns Of Diatomic Molecules, Russell A. Bonham, Jerry Peacher May 1963

Theory Of The Effect Of Temperature On The Electron Diffraction Patterns Of Diatomic Molecules, Russell A. Bonham, Jerry Peacher

Physics Faculty Research & Creative Works

The effect of temperature on the electron diffraction pattern of a diatomic molecule is considered from the standpoint of the simple kinematic scattering theory utilizing a quartic vibrational potential. The potential is obtained by an expansion of ħ2J( J+1)/2μr2+D exp[-2a(r-re)]-2D exp[-a(r-re)] about its minimum value r0. The second-order wavefunction for the nth vibrational and 7th rotational state of the system has been obtained, and expressions for the electron diffraction quantities rg, le 2, and M (s) have been computed. General results for the quantity M ...